About the PeSIT protocol

What is PeSIT?

PeSIT is an end-to-end public protocol designed to provide a reliable and normalized interface for user applications to exchange files and messages between heterogeneous systems, irrespective of the network communication type. You can use the PeSIT protocol on TCP/IP as well as some proprietary communication networks.

In this PeSIT protocol sub-book we'll first review PeSIT features, then discuss how PeSIT works in Transfer CFT, the processes involved in partner interactions, and lastly provide a description of PeSIT PI codes in a Transfer CFT context.

Why use PeSIT?

PeSIT features available for Transfer CFT include:

File transmission

File transmission, also known as file-writing, enables you to transfer data to a remote partner, provided that you have established a logical link between the two users.

File reception

File reception, also known as file- reading, enables you to transfer file data from a partner that is represented by a remote partner.

Setting synchronization points

The data sender can initiate sequentially numbered synchronization points during the transfer. The data receiver can acknowledge the synchronization points to confirm that the data transferred up to that point has been correctly received and saved. This mechanism is used to restart a transfer after an incident.

When you establish the logical connection between partners, the two partners can negotiate the following:

  • Synchronization acknowledgement window
  • Interval between synchronization points
  • Whether re-synchronization is allowed

Restarting interrupted transfers

Transfer restart enables you to restart a transfer interrupted before its completion. The interruption closes the file and disables the protocol and network connections. It is always the Initiator who initiates the restart and the Receiver who decides from which synchronization point the transfer is to be restarted.

Dynamic synchronization

Dynamic synchronization allows you to ask the partner to restart the transfer from a previous synchronization point, if an incident was encountered during data transfer. The file remains open during this operation, which can be initiated by either Initiator or Responder.

Temporary suspension of transfer

Transfer suspension allows you to suspend the current transfer (close and deselect the file) but retain the active connection between the Initiator and the Responder. The suspended transfer will be restarted later.

Data compression

Data can be compressed in order to reduce the size of data actually transferred.

Two types of compression are available in PeSIT:

  • Horizontal compression: deletes repeated characters in a logical record
  • Vertical compression: transmits only that data which differs from the previous record

Generic file selection

When an existing file is remotely selected for read access, the file name sent by the Initiator is no longer just a nominative reference. With PeSIT, it may also be a set of criteria that the server uses to select files. File selection can also be generic. The partner partners are responsible for handling the fact that several files may meet the given selection criteria.

Two-way transfers over the same logical connection

The PeSIT protocol allows only one file transfer in a given session at a time. Nevertheless, Transfer CFT can perform several concurrent transfers either as: 

  • Consecutive transfers within the same session
  • Several simultaneous file transfers on different sessions in both directions

End-to-end response acknowledgment messages

Message transfer which enables the transmission of application messages of arbitrary length, or end-to-end response acknowledgment messages.

This operation enables items of relatively small information to be exchanged between the partners. A message is accompanied by a minimum of service information and may, for example, be used to acknowledge the correct processing of a received file. Transfer CFT enables you to transmit 512-character user messages (between two Transfer CFTs the limit is 4096 characters).

Additionally, Transfer CFT provides negative acknowledgment capabilities.

Relay store-and-forward mode

The relay store-and-forward mode is available with automatic routing from one partner to another via intermediate partners.

PeSIT diagnostic codes

PeSIT protocol diagnostic codes provides PeSIT reason and diagnostic code information, error codes, and FPDU values.

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